This is what you need to get started:
http://www.smashboards.com/showthread.php?t=42749
That should cover everything you need to know in order to get started.
Now, for Samus specific:
http://www.smashboards.com/showthread.php?t=98477&highlight=samus
A pretty knowledgeable player we on the marth boards call UMBC describes pretty good strats and techniques on beating Samus.
As for videos of professional players:
http://www.smashboards.com/showthread.php?t=89158
This is a video archive of a lot of good players. Kizzu, although has amazing combos and is one of the top players in his country, shouldn't be your primary example of how to play, no matter how flashy he is. Also, another thing I should say is that watching these vids won't make you amazing. You'll learn a few tricks, and get a basic understanding of basic applications of advanced techniques, but because your not understanding what the players are thinking, don't really base your playstyle off of thiers.
This next thread is amazing for any questions or concerns you have. Honestly, I can personally say that this thread will probably help you the most.
http://www.smashboards.com/showthread.php?t=102763
Basically, this thread was started by a player named Emblem Lord, who cleaned up the marth boards pretty well. If you ask questions about ANYTHING in that thread, and you should have a lot of questions considering how new you are, people will answer it. And if no one does, I'll help as much as I can. A pro player named Cactuar also answers questions in that thread, so there's definitely reliable advice given there.
Ok, lastly, I personally like to look this thread over every once in a while.
http://www.smashboards.com/showthread.php?t=102436
Basically, it will give you good approaches with Marth, and should help you get started understanding when and where and how to attack your opponent. The same person that made the Q&A thread made this thread, so it's pretty reliable.